Can't 'Unpress' Key on MacBook Air Keyboard

What is the exact model of this laptop? You can get this information by clicking the Apple menu and selecting "About This Mac".

If it is a butterfly keyboard, then maybe some dirt is stuck in the butterfly mechanism. Here is an Apple article with instructions for cleaning a laptop keyboard. It is very important to make sure to keep the can of compressed air completely upright, otherwise you will damage the laptop with cold wet propellant.

Is the key cap snug or is it loose? A loose key cap can cause the key to bind. Or if the key cap was not properly reattached will cause it to bind. Key caps are easily damaged.

If this keyboard uses a scissor mechanism as opposed to the butterfly mechanism, then most likely the scissor mechanism has some liquid residue on it causing it to bind. Also make sure there is no residue along the inside edges of the key bay, on the ends of the key cap, or on the pivot points on the underside of the key cap.